Landscapes of the Capes


The Capes catchments area includes Cape Naturaliste in the north and Cape Leeuwin in the south and extends inland to include the catchment of the Margaret River, as well as that of a number of smaller creek systems draining westwards to the Leeuwin-Naturaliste coast. The Capes catchments areas encompasses portions of four national parks, including the Leeuwin-Naturaliste National Park featuring some of the finest cave systems in Australia and also includes the popular Boranup Karri Forest.

Land

The geology of the catchments area is comprised of two principal elements: the dominant Leeuwin-Naturaliste Ridge and east of this, across the Dunsborough Fault, the southern extension of the Perth Basin known as the Bunbury Trough. The Dunsborough Fault is aligned north-south between the townships of Dunsborough and Augusta.

The Capes catchment areas can be divided into three physiographic regions; Blackwood Plateau, Margaret River Plateau and Leeuwin-Naturaliste Coast. Within these three regions, six land systems (areas with recurring patterns of landform, soils and vegetation) occur (Tille and Lantzke, 1990, and Churchward, 1992).

Learn more about the Blackwood Plateau, Margaret River Plateau and Leeuwin-Naturaliste Coast

Blackwood Plateau

In the eastern portion of the catchments area the Blackwood Plateau is a gently undulating plateau of rolling low hills and rises formed on the laterised surface of the Bunbury Trough. The northern edge of the Blackwood plateau is formed by the Whicher Range which abuts the Swan Coastal Plain, beyond and to the north of the Capes catchments area. Land Systems – Blackwood Plateau System; Treeton Hills System; Goodwood Valleys System.

Margaret River Plateau

Further westwards, and separated from the Blackwood Plateau by the Dunsborough fault, the Margaret River Plateau is a gently undulating 5-15 km wide area extending from Dunsborough to Augusta. It is dissected by a series of valley systems, including the Margaret River, and has formed on the underlying granitic and gneissic basement rocks of the Leeuwin Block. Land Systems – Cowaramup Uplands System, Wilyabrup Valleys System.

Leeuwin-Naturaliste Coast

This is a narrow 0.2 to 0.56 km wide strip of land which runs along the coast between Cape Naturaliste and Cape Leeuwin. It comprises a discontinuous ridge of Tamala Limestone with prominent rounded hills ranging between 160 m and 200 m in height and the underlyling Leeuwin Black granite exposed in places.

The Leeuwin-Naturaliste Ridge is included in the Register of the National Estate (Giblett & Webb, 1996) and contains hundreds of caves of significance due to the quality of the formations and the cultural and fossil remains they contain. The coastline west of the ridge comprises steep limestone and granite cliffs interspersed with sandy bays and steep sand dunes between rocky headlands. Land system – Gracetown Ridge System.

Natural Waterways

The Margaret River is the only true river system within the Capes catchments. The river is approximately 60 km long with a catchment of 470 sq km (Pen, 1999). It flows from headwaters within forested portions of the Blackwood Plateau and then through mostly cleared farmland and areas of rural-residential development to emerge at the coast near Prevelly. In its middle reaches it passes through national park and the Margaret River township.

The Margaret River Action Plan (CCG, 2003) identified the river to be in reasonably good condition for much of its length, retaining many of the features of a healthy waterway. The river’s riparian vegetation has been severely impacted on by clearing, stock grazing and watering, and weed invasion. The upper reaches, within State Forest, has considerable natural values. The river supports the only known population of the critically endangered Margaret River Hairy Marron (Cherax  tenuimanus) which is also recognised as a Regional Priority. Learn more.

Other smaller watercourses within the Capes catchments area includes (north to south):

  • Yallingup Brook
  • Gunyulgup Brook
  • Wyadup Brook
  • Quininup Brook
  • Wilyabrup Brook Learn more
  • Biljedup Brook
  • Veryiuca Brook
  • Miamup Brook
  • Cowaramup Brook
  • Ellen Brook Learn more
  • Boodjidup Brook
  • Calgardup Brook
  • Turner Brook

The SWCC Regional Strategy identifies ‘the streams of the Leeuwin Ridge’ as a Regional Priority. This includes all the streams above and are discussed further here.

Wetlands

Many of the wetlands within the Capes catchments area have been cleared or modified by drainage. Therefore, any remaining within remnant vegetation, national park or State Forest have important values.

The Leeuwin-Naturaliste Ridge supports a range of unique wetland habitats, including the Cape Leeuwin wetlands system covering an area of 20 ha to the south-west of Augusta. This wetland system provides habitat for the largest known population of the Leeuwin Freshwater Snail (Austroassiminea letha). Learn more. It is also listed in the Directory of Important Wetlands in Australia (ANCA, 1996).

Other significant wetlands include:

  • Lake Davies system – comprising 3 small swamps and a small lake within the Leeuwin-Naturaliste National Park near Hamlin Bay;
  • Devils Pool – on Boodjidup Brook;
  • Margaret River swamps – in the upper forested reaches of that river system;
  • Turner Brook wetlands – a 200 ha area of floodplain on Turner Brook; and
  • Lagoons formed in the lower reaches of Wilyabrup Brook and Margaret River.

Groundwater

The Capes catchments encompass portions of two  declared groundwater management areas, Busselton-Capel generally north of Margaret River, and Blackwood to the south.

There is limited availability of groundwater in western portions of the catchments area (Leeuwin-Naturaliste Ridge) due to the lack of sedimentary aquifers. However within the eastern portion (Blackwood Plateau) there are two aquifers of considerable size, the Leederville and the Yarragadee. Both are presently utilised, with the possibility of significantly increased abstraction from the Yarragadee aquifer. Since many wetlands and stream systems are dependent on groundwater inputs, consideration of hydrological linkages between surface and groundwater systems is particularly important in determining allocation of water resources.

Biodiversity

Areas Managed for Conservation

The Capes catchments encompass portions of four national parks and one conservation park managed by the Department of Parks and Wildlife (DPaW formerly DEC).

  • Leeuwin-Naturaliste National Park (15,493 ha) – is the most visited national park in the state; includes cave systems and Boranup Karri Forest.
  • Bramley National Park(4020 ha) – adjoining the Margaret River townsite.
  • Forest Grove National Park (1400 ha) – contains a number of poorly reserved vegetation complexes.
  • Yelverton National Park (790 ha) – contains a number of poorly reserved vegetation complexes.
  • The Rapids Conservation Park (1145 ha) – encompasses pools and swamps within the Upper Margaret River.

Vegetation

Approximately 66% of the Capes catchments area is covered in native vegetation, and 29% of this occurs in areas reserved for conservation (Hopkins, Morgan & Shepherd, 2001). In the eastern portion there is a large contiguous patch of medium jarrah-marri forest (mainly within State Forest, National Park or conservation reserve) with narrow links to the coast. Along the coastline, extending to about 5 km inland, there is fairly contiguous coastal heath and shrubland, largely within the Leeuwin-Naturaliste National Park. However, within the the central portion of the catchments area native vegetation is heavily fragmented, with much of the cleared land used for agricultural production, particularly grazing.

Jarrah-marri forest is the most widespread of the 26 vegetation communities identified in the catchments area. 70% of the remaining jarrah-marri forest is within DPaW estate with 21% of this reserved for conservation. Approximately 57% of the remaining karri forest is reserved for conservation.

There are a number of other vegetation communities in the catchments area with only a very small percentage of their remaining extent in areas reserved for conservation. They include: sedgelands; reed swamps occasionally with heath; low paperbark woodland; low jarrah woodland; and low forest of jarrah-marri (Hopkins, Morgan and Shepherd, 2001).

Ecological Linkages

Although only a small percentage of the catchments area, vegetation remaining within large and small reserves provide important landscape functions. Vegetation (remnant and revegetation), natural waterways and wetlands located outside of these areas also provide important functions, acting as stepping stones and linkages between these small and large conservation reserves. Regional ecological linkages have been identified across the entire South West NRM region including the Capes catchments area and can be learned about here. Linkages have also been identified by the Cape to Cape Catchments Group at a more localised scale.

Flora

In the Capes catchments area, concentrations of endemic flora are particularly noted for the Whicher Range (in which the Margaret River swamps and upper reaches occur) and the Leeuwin-Naturaliste Ridge (Lyons et al., 2000).

As of 2001 there were 30 plant species classified as Declared Rare Flora (DRF) within the Capes area. In 2005 there were 76 ‘priority’ flora species listed in the Augusta-Margaret River Shire and 136 ‘priority’ species listed in the Busselton Shire in 2004. Not all of these species will occur within the Capes catchments area and there will be duplication of species across shire boundaries.

Fauna

The Capes catchments area supports a diverse range of fauna species. Approximately 24 mammal species and 44 reptile and amphibian species are known from the area, and there are at least fifty-two species of birds (CCG, 2004a). While some species such as the Western Grey Kangaroo are common, many others are now rarely seen or are restricted in range and have been afforded special protection status (Wildlife Conservation (Specially Protected Fauna) Notice 2014); including:

Schedule 1 – Fauna that is rare or likely to become extinct

  • Western Ringtail Possum (EN)
  • Brush-tailed Phascogale (VU)
  • Chuditch (VU)
  • Woylie (CR)
  • Baudin’s Black Cockatoo (EN
  • Carnaby’s Black Cockatoo(EN)
  • Red-tailed Black Cockatoo (VU)
  • White-bellied frog (CR) Learn more
  • Orange-bellied frog (VU) Learn more
  • Cape Leeuwin Freshwater Snail (VU) Learn more
  • Margaret River Hairy Marron (CR) Learn more
  • Margaret River Burrowing Crayfish (CR) Learn more
  • Dunsborough Burrowing Crayfish (EN) Learn more
  • Carter’s Freshwater Mussel (VU)

Priority Fauna (DPaW 2014)

  • Quenda (P5)
  • Rakali or Water Rat (P4)
  • Western Brush Wallaby (P4)

To find out the definition of the conservation codes click here.

Streams of the catchments area are habitat for freshwater fishes. Species which have been identified as threatened or of conservation significance (Horwitz et al., 1997) include the black-striped minnow (P3), Balston’s pygmy perch (VU), western mud minnow (VU), western pygmy perch, western minnow, nightfish and the pouched lamprey (P1).

Freshwater crayfish native to WA are endemic to the south-west (Morgan and Beatty, 2005) and include the Margaret River ‘hairy marron’. The hairy marron is critically endangered as its abundance in the Margaret River has been severely reduced through competition with the smooth marron, introduced into the river in the 1980s. Other freshwater crayfish occurring, or likely to occur within the area, include the Margaret River Burrowing Crayfish (CR) and the Dunsborough Burrowing Crayfish (EN).

There are also a number of threatened snails within the Capes catchments, including the Cape Leeuwin freshwater snail (VU), which is an inhabitant of the Cape Leeuwin wetlands system and Ellen Brook.

Threatened Ecological Communities

Aquatic root mat communities

The rare and complex aquatic rootmat communities of the limestone caves beneath the Leeuwin-Naturaliste Ridge are home to a rich array of wildlife. These communities are made up of freshwater crayfish, insects, crustaceans, water bears (tardigrades), rotifers (tiny aquatic organisms), mites, microscopic worms and fungi which exist in the mat of eucalyptus and peppermint tree roots that pervade the soil in search of water from permanent underground streams.

Glimpses thumbnailMore information on the Commonwealth listed communities can be found on the Glimpses into disappearing landscapes website here. Copies of the book “Glimpses into disappearing landscapes. Nationally Listed Threatened Ecological Communities of the South West Region” are also available through SWCC.

Augusta microbial structures – Tufa colonies

These rimstone pool and cave structures are formed by fresh water and microbial activity (bacteria/algae/cyanobacteria) on marine shorelines. They comprise stromatolitic and ill-defined structures composed of calcium carbonate. They are also referred to as ‘Tufa communities’ and are an important source of palaeo-environmental information. Most occurrences are within the Leeuwin-Naturaliste National Park, however they are still at risk from changed hydrological regimes and trampling. Learn more.

Marine

There are a broad range of natural and artificial benthic habitats along the Capes coast that support a rich diversity of marine flora and fauna. These habitats include granite and gneiss reefs, rock pools, sandy beaches and small embayments, limestone reef platforms and shipwrecks.

A high degree of endemism and diversity among marine species is present and the sheltered embayments, offshore reefs and headlands provide habitat for distinct communities of seagrasses and marine algae.

The marine environment of the Capes catchments area is included within the Ngari Capes Marine Park. Learn more.

Coast

The Cape to Cape coast provides scenic quality and a range of recreational opportunities. The long beaches, sheltered bays, good fishing, world-class surfing and the dramatic coastal cliffs combine to give the Leeuwin-Naturaliste region its character.

Owing to the location and extent of the Leeuwin-Naturaliste National Park, access to the coast has been kept to a relative minimum and this has resulted in the maintenance of a ‘natural’ scenic landscape for much of the coast. A number of planning documents exist addressing the protection of the coastal values and management of land use development along this coastal strip.

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